Several follow-up studies of young autistic children in an intensive behavior modification treatment program are proposed. Study I is a multiple baseline across subjects design that will examine the differential contributions of quantity and quality of treatment to the progress of autistic children currently receiving limited (10 hours per week) behavior therapy. The study seeks to determine whether 40 or more hours of behavior therapy weekly is sufficent to produce substantial changes in both behavioral excesses and deficits present in autistic children; or whether the 40 plus hours must include the use of aversive behavioral interventions in order to produce the desired behavior changes and treatment outcome. Study II is a follow-up analysis of ten "recovered" autistic children who previously participated in this research in the intensive (40 or more hours per week) treatment group. All are currently or are projected to be in normal classroom placements, in the normal range on psychological tests, and functioning well according to behavioral measures and parental reports. The ten autistic children along with ten randomly selected classmates will be referred for a complete psychological assessment battery to a psychologist blind to the children's diagnostic histories. The study seeks to examine the potential residual deficits in language, cognitive, play, social, emotional, and behavioral functioning of recovered autistic children and the implications for future treatment, prognosis and understanding of the disorder of autism. The studies together seek to clarify the essential aspects of a comprehensive behavioral treatment program that has met with considerable success, and to relate this treatment approach to the prognossi for autistic children who are so intensively treated.